EP1744236B1 - Configuration of components when changing from a low-power to a normal-power consumption mode - Google Patents

Description

The invention relates to the configuration of components or entire parts of a circuit arrangement which is necessary in the event of a transition from a low-power operating mode to a normal-power operating mode. In particular, the invention relates to such a configuration of a control unit which controls the accesses of a plurality of processors to a memory unit in a processor memory system. Furthermore, the invention relates in particular to the restoration of the contents of volatile memory elements of a circuit arrangement when returning to a normal power operating mode from a low-power operating mode.

In the present patent application, a low-power operating mode is understood to mean an operating mode in which the energy requirement of the relevant component or circuit is reduced and, accordingly, the component or circuit can not perform the functions for which it or they are actually designed are. A low-power operation mode is, for example, a standby mode. Under a low-power operating mode is also a temporary disconnection from the supply voltage to understand. In a normal power operating mode, the functions of the relevant component or the relevant circuit arrangement, for which the component or the circuit arrangement are designed, can be performed.

In a processor memory system that is designed so that multiple processors can access a memory unit, the problem arises that a control unit, which controls the accesses of the processors to the memory unit loses its register values during a temporary shutdown into a low-power operating mode. In a later "waking up" of the control unit, these register values of the control unit are therefore no longer available. The configuration state of the control unit is therefore undetermined after starting up in the normal power operating mode. However, a precise configuration state of the control unit is necessary because only such a condition ensures that the control unit interacts correctly with the memory unit and that the data outputs of the control unit, via which the processors obtain the requested data, are set up in the correct way. It is therefore necessary, after a return of the control unit to the normal power operating mode, to load the data required for its configuration back into the registers of the control unit.

In conventional processor memory systems, the register values needed to configure the controller are stored in nonvolatile memory and are loaded into the controller after returning the controller to normal power mode of operation. This process is controlled by one of the processors. A disadvantage of this approach is that the processor responsible for the configuration of the control unit must itself be in a normal power operating mode for each such configuration operation. For example, it may be the case that all the processors and the control unit are in a low power mode of operation. As soon as one of the processors is "woken up" and this processor needs data from the memory unit, not only the control unit but also the processor responsible for its configuration must be returned to the normal power operating mode. Thus, in such a case, this processor can not be left in the low power mode of operation. This requires an increased Power consumption of the processor memory system. Furthermore, a high software effort for controlling the processor memory system is required.

The problem described above arises not only in processor memory systems, but more generally in circuit arrangements having a circuit portion which can be shut down to a low power mode of operation. In a later activation of this circuit part, the contents of volatile memory elements and registers are no longer available. In order to restore the state that existed before shutting down to the low-power mode of operation, the contents of volatile memory elements and registers must be loaded before shutdown into a memory that retains its contents during the low-power mode of operation of the circuit part concerned. After restoring the normal power mode of operation, the previously cached data may be transferred back to the corresponding memory elements and registers of the circuit portion concerned. The described buffering of the data and its later writing back to the volatile memory elements and registers is performed by a processor in conventional circuit arrangements. This requires increased power consumption and complex software.

In the publication US 6,230,274 B1 discloses a processor memory system comprising a processor, a memory unit, and a memory controller. The memory controller includes a configuration unit that loads configuration data from a buffer after exiting a low power mode of operation, configures the memory controller in accordance with this loaded configuration data, and restores the operational state prior to entering the low power operating mode of the memory controller. However, because the configuration unit is part of the hardware the memory controller is formed, the configuration unit loses the cached configuration data with the entry of the memory controller in a low-power operating mode. Upon re-entry into a normal power operating mode, therefore, additional time and computational power must be used to re-supply the configuration unit with the necessary configuration data.

The object of the invention is therefore to provide a circuit arrangement of which at least a part may temporarily be in a low-power operating mode. In a subsequent startup of this circuit part should be able to restore the original state of the circuit part with relatively little effort. In particular, a processor memory system is provided with a control unit for controlling the accesses of the processors to the memory unit, wherein the control unit can be temporarily transferred to a low-power operating mode and the processor memory system has a lower power consumption as well has less software complexity than conventional systems. Furthermore, a method for changing a processor of the said processor memory system in the low-power operating mode is to be specified. In addition, a method for returning the control unit of the processor memory system in the normal power operating mode is to be specified.

The object of the invention is based solved by the features of the independent claims 1, 13 and 15. Advantageous developments and refinements of the invention are specified in the subclaims.

The processor-memory system according to the invention comprises at least one processor, a memory unit, at least a first memory control unit and a configuration unit.

If the processor memory system has a plurality of processors, the memory unit is shared by the processors. The at least one first memory control unit is arranged between the at least one processor and the memory unit and controls the accesses of the at least one processor to the memory unit, ie the at least one processor accesses the data stored in the memory unit via the at least one first memory control unit. The configuration unit has the task of configuring the at least one first memory control unit when changing over the at least one first memory control unit from a low-power operating mode to a normal-power operating mode. The configuration unit is preferably designed only for this task and has no further tasks. The configuration unit is realized as a hardware component. In the present patent application, a hardware component is understood to mean a component which is not able to process machine codes. In contrast, on software components, such as on processors, programs running in machine code.

In the processor memory system according to the invention, the configuration of the at least one first memory control unit when returning from a low to a normal power operating mode is performed by a hardware unit and not by a processor as in conventional processor memory systems. Thus, in contrast to conventional processor memory systems, the at least one processor according to the invention is released from this task. As a result, when the at least one first memory control unit returns to the normal power operating mode, the at least one processor can basically remain in a low-power operating mode. As a result, this reduces the power consumption of the processor memory system and reduces the complexity of the software running on the processors.

The configuration unit preferably contains a data transfer unit and a buffer. The data transfer unit is designed such that, when the at least one first memory control unit is changed from a low-power operating mode to a normal-power operating mode, first configuration data, which has previously been stored in the buffer, is written to registers in the at least one first memory control unit. The first configuration data serve to configure the at least one first memory control unit.

The data transfer unit is implemented in hardware. The cache may be a static RAM, a FIFO memory, or a similar memory device suitable for storing the first configuration data. In particular, the buffer must not lose its memory contents during a low-power operation of the at least one first memory control unit. Consequently, the cache is either designed to maintain its contents even during a low power operation, or not shut down itself during a low power operation of the at least one first memory controller.

Furthermore, the data transfer unit preferably transfers first configuration data from the registers of the at least one first memory control unit into the buffer memory before a shutdown of the at least one first memory control unit into a low-power operating mode. This measure makes it possible to reconstitute the configuration of the at least one first memory control unit that existed before shutdown after the low-power operating mode has ended.

According to a particularly preferred embodiment of the invention, a second control unit is provided, which controls the configuration unit. The second control unit is realized in particular by a hardware unit. The second control unit may, for example, transmit control signals to the configuration unit in order to cause them to carry out a data transfer between the at least one first memory control unit and the buffer, which is necessary due to a change of the operating mode.

A further preferred embodiment of the processor-memory system according to the invention provides that the configuration unit or optionally the data transfer unit can be programmed.

Preferably, it may be provided that a plurality of sets of first configuration data are stored in the buffer. This measure makes it possible to operate the at least one first memory control unit in different normal power operating modes, the normal power operating modes are each characterized by different sets of first configuration data.

For example, which of the sets of first configuration data is loaded into the registers of the at least one memory controller upon a return to the normal power mode of operation may be set prior to shutting down to the low power mode of operation. A corresponding control information is then stored in the buffer. Alternatively, it can also be provided that this control information is generated by the second control unit when returning to a normal power operating mode.

Furthermore, it is advantageous to select a processor from the plurality of processors, which is the only processor authorized to configure the configuration unit or optionally the data transfer unit. This task may be, for example, that the processor determines that the values of which registers are written from the at least one first memory control unit in the cache.

The selected processor may preferably generate a plurality of sets of second configuration data for configuration of the configuration unit and the data transfer unit, respectively. These second configuration data sets are stored in particular in the cache. This measure makes it possible, for example, to provide a separate second configuration data record for each of the processors. If only one processor is woken up while the remaining processors remain in a low-power mode of operation, the at least one first memory controller must be configured based on a particular second configuration record only to the extent necessary for the operation of the awake processor.

In this context, it is particularly advantageous if the alert processor can select one of the second configuration data sets.

The data transfer unit can be realized for example by a DMA (Direct Memory Access) controller.

Preferably, the memory unit and the at least one first memory controller are always in a low-power mode of operation at the same time. This reduces the power requirement of the processor memory system according to the invention.

The first method according to the invention serves to change at least one processor of the processor-memory system according to the invention from a low-power to a normal-power operating mode. It is assumed that the at least one first memory controller is in a low power mode of operation at the beginning of the process. For this reason, first the at least one first memory control unit is converted into the normal power operating mode. For this purpose, the at least one first memory control unit is supplied with a supply voltage in a first method step, and in a second method step, the at least one first memory control unit is configured by the configuration unit. After all the prerequisites for a normal power operation of the at least one first memory control unit are met, the operating mode of the at least one processor can be changed from a low-power to a normal-power operating mode and the at least one processor can now access the memory unit via the at least one first memory control unit access.

The first method according to the invention ensures that the relevant processor only accesses the memory unit when the at least one first memory control unit is fully operational.

Preferably, the transfer of the at least one first storage control unit into the normal power operating mode is initiated by a control signal generated by the second control unit.

The second method according to the invention makes it possible to change the at least one first memory control unit of the processor-memory system according to the invention from a normal-power operating mode into a low-power operating mode. In a first method step, the first configuration data present in the registers of the at least one first memory control unit is written into the buffer memory. In a second method step, the at least one first memory control unit is disconnected from its supply voltage.

The first method step is preferably started by a control signal generated by the second control unit.

Another aspect of the invention relates to a circuit arrangement having a circuit portion having memory elements that lose their memory contents in a low power mode of operation. Furthermore, the circuit arrangement according to the invention contains a memory unit which, in contrast to the memory elements of the circuit part, retains its memory content during a low-power operating mode of the circuit part. Furthermore, a DMA controller is provided, which is designed to write the data stored in predetermined memory elements of the circuit part prior to a change of the circuit part from a normal power operating mode to a low power operating mode in the memory unit and this data after the return of the circuit part in to return the normal power mode of operation back to the memory elements.

The circuit arrangement according to the invention relieves a processor, which is responsible in conventional circuit arrangements for the data transfer in the course of a change of the operating mode. This reduces chip area, power consumption and software costs. Furthermore, the DMA controller causes no additional effort, since it is provided in most microcontroller systems anyway.

A particularly preferred embodiment of the circuit arrangement according to the invention provides two lists or tables which contain information about the data transfers to be undertaken during an operating mode change. A first list includes the information required to change the circuit part from the normal power operating mode to the low power operating mode. A second list concerns the reverse case, namely a change of the circuit part from the low-power operating mode to the normal-power operating mode.

The two lists contain, for example, information about the start and destination addresses of the data transfers to be executed, details of the incremental operations with respect to the start or destination addresses after an executed data transfer, and details of the number of data transfers to be executed.

The first list and / or the second list are preferably stored in the memory unit. This ensures that the two lists will be available after the low-power operating mode has ended.

The memory elements of the circuit part that lose their memory contents in a low-power mode of operation may be, for example, volatile memories and / or registers.

Preferably, a hardware unit or a processor is provided, which is or which is designed to control signals prior to a change of the circuit part from a normal power operating mode to a low power operating mode and / or after the return of the circuit part to the normal power operating mode, causing the DMA controller to perform the necessary data transfers.

Furthermore, advantageously, the DMA controller itself can also be converted into a low-power operating mode. In this case, the DMA controller must be configured to load the configuration data needed for its configuration from the memory unit when booting from the low power mode of operation.

Fig. 1

ein Blockschaltbild eines Prozessor-Speicher-Systems 1 gemäß dem Stand der Technik;

Fig. 2

ein Blockschaltbild eines Prozessor-Speicher-Systems 10 als Ausführungsbeispiel des erfindungsgemäßen Prozessor-Speicher-Systems;

Fig. 3

ein Ablaufdiagramm zur Veranschaulichung der Funktionsweise des in Fig. 2 gezeigten Prozessor-Speicher-Systems 10;

Fig. 4

ein detaillierterer Ausschnitt aus dem in Fig. 2 gezeigten Blockschaltbild des Prozessor-Speicher-Systems 10; und

Fig. 5

ein Blockschaltbild einer Schaltungsanordnung 300 als Ausführungsbeispiel der erfindungsgemäßen Schaltungsanordnung.

The invention will be explained in more detail below by way of example with reference to the drawings. In these show:

Fig. 1

a block diagram of a processor memory system 1 according to the prior art;

Fig. 2

a block diagram of a processor memory system 10 as an embodiment of the processor memory system according to the invention;

Fig. 3

a flow chart illustrating the operation of the in Fig. 2 shown processor memory system 10;

Fig. 4

a more detailed excerpt from the in Fig. 2 shown block diagram of the processor memory system 10; and

Fig. 5

a block diagram of a circuit arrangement 300 as an embodiment of the circuit arrangement according to the invention.

In Fig. 1 a block diagram of a conventional processor memory system 1 is shown. The processor memory system 1 consists of processors A, B and C, an SDRAM 2 and an SDRAM controller 3. The SDRAM controller 3 is connected between the processors A, B and C and the SDRAM 2.

The processors A, B and C use the SDRAM 2 as a common memory unit. The SDRAM controller 3 controls the accesses of the processors A, B and C to the SDRAM 2. The data exchange of the processors A, B and C with the SDRAM 2 takes place via the data inputs and outputs Data A, Data B and Data C of the SDRAM Controller 3. In order to enable data transmission and control, the SDRAM controller 3 has an access and control unit 4. The access and control unit 4 is connected to registers 5 in which configuration data are stored via a control input and output control. The configuration data stored in the registers 5 ensure correct interaction of the SDRAM controller 3 with the SDRAM 2. In addition, the data inputs and outputs Data A, Data B and Data C are configured using the configuration data. At the in Fig. 1 represented processor memory system 1, the configuration data is generated by the processor A and written to the register 5.

If the SDRAM controller 3 is in a low-power operating mode, ie in a stand-by operating mode, for example, and is "woken up" because, for example, one of the processors A, B or C wants to access the SDRAM 2 the configuration data from the processor A are rewritten to the registers 5 because during the low power phase of the SDRAM controller 3 the contents of the registers 5 have been cleared. In order to write the configuration data to the registers 5, the processor A must be in a normal power operating mode. The processor A is so - if he is to this Time is in a low power mode of operation - also be "woken up". The processor A must therefore return to its normal power operating mode whenever the entire processor memory system 1 is in a low power mode of operation and one of the processors B or C wants to access the SDRAM 2.

In Fig. 2 a processor memory system 10 is shown as an embodiment of the processor memory system according to the invention. Since some components of the processor memory systems 1 and 10 are identical, these components are in the Fig. 1 and 2 provided with the same reference numerals. The SDRAM 2 of the processor memory system 10 is in Fig. 2 not shown.

In the processor memory system 10, the processor A is still the task to generate the configuration data for the SDRAM controller 3 and store them in the registers 5. Unlike the in Fig. 1 However, when the SDRAM controller 3 returns to the normal power operating mode, the configuration data is not written back to the registers 5 by the processor A in the conventional processor memory system 1 shown in FIG. Rather, this data transfer is performed in the processor memory system 10 by a data transfer unit (save-restore engine) 11. The data transfer unit 11 is formed as a hardware unit.

So that the data transfer unit 11 can also have the configuration data after a low-power phase, the configuration data are written from the data transfer unit 11 into a data shadow store 12 before the SDRAM controller 3 shuts down from a normal-performance to a low-power operating mode. When the SDRAM controller 3 returns to the normal power operating mode, the configuration data is turned off the intermediate memory 12 back into the registers 5 of the SDRAM controller 3 written back.

The data transfer unit 11 is signaled an operating mode change of the SDRAM controller 3 by a control unit (power state machine) 13. The control unit 13 is also implemented in hardware. Upon receiving a control signal from the control unit 13, the data transfer unit 11 can autonomously perform the required read / write operations between the registers 5 of the SDRAM controller 3 and the latch 12.

The intermediate memory 12 has registers 12.1 to 12.n in which the register values loaded from the registers 5 of the SDRAM controller 3 are stored. In order to ensure that the registers 12.1 to 12.n do not lose their register contents during a low power mode of operation of the SDRAM controller 3, the latch 12 is not disconnected from its power supply during these periods. The buffer 12 may be implemented, for example, as a static RAM or as a FIFO memory.

It can be provided that a plurality of sets of configuration data are stored in the buffer 12, which can be loaded into the registers 5 of the SDRAM controller 3. This measure makes it possible to operate the SDRAM controller 3 in various normal power operating modes.

For example, which of the sets of configuration data is loaded into the registers 5 upon a return to the normal power mode of operation may be set prior to shutting down to the low power mode of operation. A corresponding control information is then stored in the buffer 12. Alternatively, it can also be provided that this control information is generated by the control unit 13 when returning to a normal power operating mode.

The data transfer unit 11 is configured by the processor A, i. the processor A specifies that contents of which registers 5 of the SDRAM controller 3 are to be transferred to the cache memory 12 upon shutdown to the low-power mode of operation and into which registers of the cache memory 12 these values are to be written. Since these configuration data of the data transfer unit 11 must not be deleted, the data transfer unit 11 must not be shut down.

Once the data transfer unit 11 has been configured by the processor A, the transitions between low and normal duty modes of operation can be performed entirely by hardware units.

In Fig. 3 are plotted in a flow chart, the process steps to be performed at transitions between a normal power operating mode 100 and a low-power operating mode 200.

First, consider the transition from the normal power operating mode 100 to the low power operating mode 200. This transition is triggered by a trigger signal. This trigger signal is either generated directly by the processor A in its function as system master processor or it is automatically generated as soon as all processors A, B and C are in a low power mode of operation.

Subsequently, the control unit 13 signals the data transfer unit 11 that the values from the predetermined registers 5 should be written into the registers of the buffer 12. This data transfer is performed by the data transfer unit 11 in a method step 101. In a subsequent method step 102, the SDRAM 2 activates its self-refresh mode. Before the supply voltage of the SDRAM controller 3 in one step 104 is turned off, the setting of the SDRAM controller 3 in a step 103 are reset. Thereafter, the low-power operation mode 200 of the SDRAM controller 3 is reached.

The transition from the low power operating mode 200 to the normal power operating mode 100 is again triggered by a trigger signal. This trigger signal is either generated directly by the processor A in its function as a system master processor or it is generated automatically as soon as one of the processors A, B and C is "woken up".

In a method step 201, the supply voltage of the SDRAM controller 3 is rebuilt. In a method step 202, the reset mode of the SDRAM controller 3 activated in method step 103 is deactivated.

Subsequently, a control signal is generated by the control unit 13 in order to indicate to the data transfer unit 11 that, in a method step 203, it is to restore the data transferred into the buffer 12 in the method step 101 back into the predetermined register 5 of the SDRAM controller 3. Thereafter, the normal power operation mode 100 of the SDRAM controller 3 is restored.

In Fig. 4 is a section of the in Fig. 2 shown processor memory system 10 shown. In this case, the data transfer unit 11 is shown in more detail.

In the present case, the registers 5 of the SDRAM controller 3 have consecutive addresses and the buffer 12 is part of a static RAM. Therefore, the data transfer unit 11 can be realized by means of a DMA controller, wherein the DMA controller transfers data from the registers 5 of the SDRAM controller 3 to the static RAM in a memory-to-memory transfer mode.

In Fig. 4 Reference numerals 14 to 17 denote interfaces of the data transfer unit 11 with the components connected to them. Via the interface 15, the data transfer unit 11 receives the control signals generated by the control unit 13, by means of which the data transfer processes described above are triggered.

Furthermore, the data transfer unit 11 has a central control logic 18 with configuration registers and a DMA channel logic 19.

It can be provided that the processor A generates a plurality of sets of configuration data for the configuration of the data transfer unit 11. These configuration data sets are stored in the cache 12. The processors A, B and C can select from the sentences stored there a sentence suitable for the respective situation.

A trigger signal indicates to the data transfer unit 11 which configuration record it should load from the buffer memory 12 into its configuration registers. The configuration of the data transfer unit can therefore also be changed by the processors B and C without the processor A being directly involved in this configuration process.

In Fig. 5 the block diagram of a circuit arrangement 300 is shown as an embodiment of the circuit arrangement according to the invention. The circuit arrangement 300 includes a DMA controller 301, which is connected between a circuit part 302 of the circuit arrangement 300 and a latch 303. Furthermore, the DMA controller 301 is connected to a control unit 304.

The circuit part 302 is designed such that it can be converted into a low-power operating mode if necessary. Since the registers and the volatile memory elements of the Circuit portion 302 in the low-power mode of operation lose their contents, this content must be cached in the cache 303 before shutting down the circuit part 302 in the low-power operating mode. This measure ensures that the cached data are available after a later "waking up" of the circuit part 302 and can be loaded again into the circuit part 302.

The DMA controller 301 arranged between the circuit part 302 and the buffer 303 has the task of carrying out the data transfers described above when the operating mode is changed. For this purpose, the DMA controller 301 has access to two lists each containing the information needed for a data transfer direction. Each list contains the start and destination addresses, the incremental operations for the start and end addresses, and the number of data transfers to be performed. Each list can also describe sequences of data transfers. In this case, the data for each data transfer block is automatically read by the DMA controller 301 one by one. The two lists can for example be stored in the buffer 303.

Once the circuit portion 302 is to be transitioned to a low power mode of operation, this is signaled to the DMA controller 301 by the controller 304, whereupon the DMA controller 301 performs the data backup described in the one list. Upon completion of this data backup operation, the circuit portion 302 may be disconnected from its supply voltage.

Upon completion of the low power phase, the DMA controller 301 again receives a control signal from the controller 304 to rewrite the previously latched data back into the registers and volatile memory elements of the circuit portion 302. Only after this process is completed is, a arranged in the circuit 300 microcontroller again access the circuit portion 302. If the microcontroller has also been shut down, the microcontroller will only be "woken up" after completion of the described data transfer.

It is also possible to shut down the DMA controller 301 itself to a low-power operation mode. In this case, the DMA controller 301 must be configured to self-configure immediately after being woken up by loading data from predetermined addresses of the cache 303 into its registers.

The control unit 304 may either be part of the microcontroller or a hardware unit.

The buffer 303 may be on the same chip as the DMA controller 301 and the circuit part 302, or on a separate chip.

The circuit arrangement 300 can be used, for example, in mobile devices whose storage elements generally consist of volatile SRAM elements. In the GSM standard, the stand-by mode is mandatory as soon as the mobile device is not in an active phase. This makes it possible to keep the battery consumption low. If the mobile device needs to be able to receive incoming calls, the duration of the active phases is typically only a few tens of milliseconds, while the inactive phases can take up to 2.5 seconds.

DRAM memory elements can preferably be used as temporary storage in mobile radio devices since they are able to buffer large amounts of data with a large bandwidth. Particularly suitable for this are low-energy DRAMs that are optimized to require little "refresh" current per bit. The inventive Circuit arrangement makes it possible to convert most of the logic circuit of the mobile device when needed in a stand-by mode of operation.

Claims (16)

1. Processor/memory system (10) comprising

   - at least one processor (A, B, C),

   - a memory unit (2),

   - at least one first memory control unit (3) for controlling accesses from the at least one processor (A, B, C) to the memory unit (2), and

   - a configuration unit (11, 12) which is in the form of hardware and is designed to configure the at least one first memory control unit (3) when the at least one first memory control unit (3) changes from a low-power operating mode to a normal-power operating mode,

   characterized in that the configuration unit (11, 12) remains in a normal-power operating mode during the low-power operating mode of the at least one first memory control unit (3).
2. Processor/memory system (10) according to Claim 1,
   characterized

   - in that the configuration unit has a data transfer unit (11) and a buffer store (12) with the data transfer unit (11) being designed such that, when the at least one first memory control unit (3) changes from a low-power operating mode to a normal-power operating mode, it writes first configuration data for the configuration of the at least one first memory control unit (3) from the buffer store (12) to registers (5) in the at least one first memory control unit (3).
3. Processor/memory system (10) according to Claim 2,
   characterized

   - in that the data transfer unit (11) is designed such that, before the at least one first memory control unit (3) changes from a normal-power operating mode to a low-power operating mode, it writes first configuration data from the registers (5) in the at least one first memory control unit (3) to the buffer store (12).
4. Processor/memory system (10) according to one or more of the preceding claims,
   characterized by

   - a second control unit (13) for controlling the configuration unit (11, 12), with the second control unit (13) in particular being in the form of hardware.
5. Processor/memory system (10) according to one or more of the preceding claims,
   characterized

   - in that the configuration unit (11, 12) or, if appropriate, the data transfer unit (11) is programmable.
6. Processor/memory system (10) according to one or more of Claims 2 to 5,
   characterized

   - in that two or more sets of first configuration data for the configuration of the at least one first memory control unit (3) are stored in the buffer store (12).
7. Processor/memory system (10) according to Claim 6,
   characterized

   - in that, before the at least one first memory control unit (3) changes from a normal-power operating mode to a low-power operating mode, control information is stored in the buffer store (12), with the control information providing information as to which set of first configuration data will be written to the registers (5) of the at least one first memory control unit (3) on returning to a normal-power operating mode, or

   - in that this control information is produced by the second control unit (13) on returning to a normal-power operating mode.
8. Processor/memory system (10) according to one or more of the preceding claims,
   characterized

   - in that a predetermined processor (A) is designed to configure the configuration unit (11, 12) or, if appropriate, the data transfer unit (11).
9. Processor/memory system (10) according to Claim 8,
   characterized

   - in that the predetermined processor (A) is designed to produce two or more sets of second configuration data for the configuration of the configuration unit (11, 12) or, if appropriate, the data transfer unit (11), and to store these sets in particular in the buffer store (12).
10. Processor/memory system (10) according to Claim 9,
    characterized

    - in that at least one further processor (B, C) is designed to select one of the sets of second configuration data for the configuration of the configuration unit (11, 12) or, if appropriate, of the data transfer unit (11).
11. Processor/memory system (10) according to one or more of Claims 2 to 10,
    characterized

    - in that the data transfer unit (11) comprises a DMA controller.
12. Processor/memory system (10) according to one or more of the preceding claims,
    characterized

    - in that the memory unit (2) is likewise in a low-power operating mode when the at least one first memory control unit (3) is in a low-power operating mode.
13. Method for changing at least one processor (A, B, C) in the processor/memory system (10) according to one or more of the preceding claims from a low-power operating mode to a normal-power operating mode, with the at least one first memory control unit (3) being in a low-power operating mode at the start of the method, comprising the following steps:

    (a) a supply voltage is applied to the at least one first memory control unit (3);

    (b) the at least one first memory control unit (3) is configured by the configuration unit (11, 12); and

    (c) the at least one processor (A, B, C) is changed from a low-power operating mode to a normal-power operating mode,

    characterized in that the configuration unit (11, 12) is in a normal-power operating mode at the start of the method.
14. Method according to Claim 13,
    characterized

    - in that the step (a) is started by a control signal which is produced by the second control unit (13).
15. Method for changing the at least one first memory control unit (3) in the processor/memory system (10) according to one or more of Claims 2 to 12 from a normal-power operating mode to a low-power operating mode, comprising the following steps:

    (a) first configuration data, which is stored in the registers (5) of the at least one first memory control unit (3), is stored in the buffer store (12);

    (b) the at least one first memory control unit (3) is disconnected from a supply voltage.
16. Method according to Claim 15,
    characterized

    - in that the step (a) is started by a control signal which is produced by the second control unit (13).

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